1. Field of the Invention
The invention relates to improving the security of metering devices against tampering and theft of services, and more particularly to means for locking in place the terminal chamber covers of bottom connected electrical meters.
2. Description of the Prior Art
Electric metering devices are available and in general use for measuring the quantity of energy and power of residential and commercial users of electricity. One common meter configuration, called a bottom connected or "A" base meter permits connection of electrical service wires or current transformer secondary leads to the meter's base or terminal block. "A" base meters are most widely used for metering electrical services of commercial and industrial customers of electric power utility companies.
Meter manufacturers have standardized the dimensions and wiring details of "A" base meters, so that a general description of those meters to which the present invention is applicable can be given.
The typical bottom connected meter is mounted on a wall of a building and held securely in place by two or more mounting screws which pass through the body of the meter from front to back. Means for displaying the measured quantity, such as kilowatt hours of energy consumed, are disposed within a transparent dome-like cover of the meter. This cover, usually of glass with a metal rim for securing it to the body of the meter, encloses not only the dials or register showing energy and/or power consumed, but also the meter's electricity measuring circuitry, all of which becomes accessible if the transparent cover is removed. The cover is screwed into position by rotation so that means on the cover's rim engage mating means on a projecting flange on the front face of the meter's body. The mounting flange is in the form of an incomplete ring with a break at its lower portion.
A terminal block to which wiring entering and leaving the meter connects is disposed below the portion of the meter covered by the transparent dome. The electrical wires are secured to the terminal block by screws located at the front of the block. The heads of these wire-securing screws are normally concealed by a terminal block cover which extends across the lower front portion of the meter, beneath the glass cover.
The terminal block cover protects the terminal block and receives a sealing bar which passes horizontally through part of the block cover from one side. The terminal block cover sealing bar has slots and/or holes to permit seals, for example, a power company's unique plastic, lead wire or padlock sealing means to be installed, so that an attempt to tamper with the meter can be detected by inspecting the integrity of the seal.
An upwardly projecting lip on the inner end of the sealing bar is positioned to interfere with rotation of the glass cover when the meter is sealed. This prevents removal of the transparent cover by unauthorized persons who might attempt to set back the meter's register or otherwise tamper with the meter in order to steal electrical service.
Although seals made of aluminum, thin wire or plastic are in common use, such seals are easily cut off, and the tamperer may attempt to replace the seal, duplicate the seal, or may simply deny having interfered with the seal.
A second very serious weakness in the security of "A" base meters is the sealing bar lip, which has as its sole purpose interference with a protrusion on the rim of the meter's transparent cover to prevent the cover's removal. The lip is made of aluminum or other soft material and is exposed to tampering because it is not concealed by the terminal block cover, so the lip can be filed, cut, ground off, etc., by a tamperer so that it no longer prevents removal of the glass cover. By damaging the sealing bar lip, an unauthorized person can gain entry to the meter's internal components without having to break the seal or remove the terminal block cover. Such tampering can be less noticeable than violation of the meter seal, and may go undetected by service personnel, such as meter readers.
It is highly desirable to prevent tampering and damage to meters and other utility equipment, so various kinds of locks have been developed for securing doors, covers, etc. One such type of lock is the barrel lock, exemplified by the lock of U.S. Pat. No. 4,040,279. Barrel locks have an overall cylindrical shape to fit within a cylindrical receptacle which has an internal recess or recesses to receive locking balls which project radially outward when the lock is in locked or engaged condition, and which are retractable when a proper key is used to "open" the lock.
The present invention relates generally to ways in which locks such as barrel-type locks can be used to secure the terminal block covers of electric meters of the type described against tampering.